Renewable energy sources, such as solar and wind farms, are becoming more economically viable as traditional fossil fuel prices continue to rise. Existing electrical power distribution (grid) infrastructure can be utilized for distributing power from renewable energy sources if the proper control system is in place for coordinating power produced with the demand of the utility. Demand for power can be measured and the demand signal can be used to control the amount of power supplied to the electrical grid by the renewable source.
Real power is generated or consumed when voltage and current are in phase. Reactive power is generated or consumed with when voltage and current are 90 degrees out of phase. A purely capacitive or purely inductive load will generally consume only reactive power (with the exception of small resistive losses) and no appreciative real power is transferred to the load. Reactive power is measured by a quantity called volts-amps-reactive, or VARs, which is a convenient mathematical quantity because apparent power is the vector sum of VARs and watts. The stability of the electrical grid is related to the generation and/or consumption of reactive power; therefore, it is usually necessary to control the reactive power output from the renewable energy source to fulfill electrical demand while providing stability for the electrical grid.
Previous reactive power management methods and systems regulate VAR commands, which are sent to wind turbines to control the instantaneous reactive power production of each wind turbine. Such methods and systems may fulfill demand and stabilize the electrical grid by generating reactive power but fail to address the short-term regulation of voltage from the power source or compensate for reactive power loss in transmission lines. Therefore, there exists a need for reactive power regulation and voltage support for renewable energy plants.